Author: José Carlos
Date: 02:56:14 08/10/01
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On August 10, 2001 at 05:37:06, Andrew Williams wrote: >On August 10, 2001 at 04:30:20, José Carlos wrote: > >> After completely rewriting my chess program (Averno), I've run into the >>null-move world, which I haddn't in old versions. >> In old Averno I had: >> >> -Reasonably good move ordering (hash move; good captures; killers; ...) >> -Transposition table >> -2 killers >> -Lazy eval >> -Check and recapture extension >> -Some out-of-check stuff in qsearch >> >> With that, I was searching 6-7 plies in blitz (in midgame) and 7-9 in >>standard. [Athlon 550] >> >> I've read some open source programs to get a clue on how to search deeper, and >>now I have: >> >> -Nullmove (tried R=3 and R=2, not yet R=2/3) >> -Futility pruning >> -Same move ordering as before >> -Same hashing scheme >> -Same 2 killers >> -Same Lazy eval >> -Check and null-threat extension >> -No out-of-check stuff in qsearch >> >> And now, I search 7-8 plies in blitz and 8-10 in standard (and the worst thing >>is that the program looks weaker than the old one!) >> That looks like a poor search depth, isn't it? So what am I missing to get, as >>most null-movers, 12-13 in standard? >> SEE? History heuristic for move ordering? ETC? Razoring? >> Sorry for _answering_ instead of _trying_ but, as I have so little free time >>to work on my program, any advice would be appreciated. >> As well, I'd like to know if, with the stuff I've implemented so far, I should >>expect a better performance. In that case, I might have a bug somewhere. >> >> Thanks in advance, >> >> José C. > >Seriously, I think the first thing you should look at is move-ordering. I find >that errors I introduce here have an enormous impact on the depth of searches. >One metric that many people use is to see what proportion of beta cut-offs in >the search are achieved on the *first* move searched at a given node. The >higher this figure the better. Aim for over 90%. > >Cheers > >Andrew Ok, I'll calculate that number tonight... José C.
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